This invention relates to hair conditioning compositions. More particularly, this invention relates to aqueous hair conditioning compositions that comprise relatively high molecular weight amine oxides at low pH's.
Hair conditioning agents assist in the control and management of hair. Conditioned hair is easily untangled and combed through after shampooing, lays orderly when dry and provides a favorable feeling to the touch. The conditioning action on hair, particularly by cationic conditioning agents, is believed to be caused by the attraction of the positively charged agent to the negative sites on hair protein resulting in the deposition of the agent onto the hair fiber.
After washing hair and during the subsequent management of the dry hair, the combing and brushing forces produce friction resulting in the accumulation on the hair's surface of immobile electrons or ions of the same charge. The hair is commonly referred to as containing static charge and displays the phenomenon of "fly-away". Such hair is unruly, will not lay flat and is considered generally unmanageable.
Ionic depositions including positively charged cationic conditioning agents can be used to dissipate static electricity by increasing the mobility of the electrostatic charges that accumulate on hair. Furthermore, the fatty nature of the cationic conditioning agent produces lubrication on the hair's surface that reduces friction resulting in both the overall lessening of accumulated electrostatic charges and the promotion of easy combing. The process by which cationic surfactants are applied to hair is referred to as conditioning the hair, and the treatment results in hair that no longer sustains a static charge and in hair that also feels soft, silky and is highly manageable.
Cationic surfactants have been used extensively as hair conditioning agents in creme rinses and shampoos, generally at pH levels below pH 7 in creme rinses and through pH 7 and above in shampoos. In the past, best results in creme rinses have been obtained with cationic surfactants that are long chain high molecular weight quaternary ammonium compounds or long chain fatty amine salts. For example, stearalkonium chloride has been widely used as a component of creme rinse hair conditioning formulations. The positive charge of the quaternary surfactant is attracted to the negatively charged surface of the hair protein; the surfactant deposits on the surface and subsequently renders the hair manageable. The long chain constituent on the quaternary surfactant coats the hair fiber giving it lubricity during wet combing and a desirable texture after drying. The longer the chain length the more active the conditioning agent is said to be; the greater the residual film deposit on hair the easier the detangling effort and the less electrostatic charge build-up and subsequent hair fly-away.
Quaternary ammonium compounds carry and maintain positive ionic charges from highly alkaline to highly acidic media. However, many industrial quaternary ammonium compounds are partially or totally unsuitable for cosmetic use because they can contain impurities which restrict use to specific pH ranges or restrict use completely. If trace quantities of deleterious quaternizing agents used in synthesis are present, the quaternary ammonium compound should not be used in cosmetics. Long chain fatty amines, which usually account as significant impurity in the quaternary ammonium compounds used for cosmetics, force the use of the quaternary ammonium compound, and the cosmetic itself, to pH's below 7. Below pH 7, the long chain amines exist as surface active salts which produce similar hair conditioning effects as surface active quaternary ammonium compounds. Above pH 7, the amine salts revert to their free organic amine state which cause them to loose their hair conditioning properties, to produce cosmetically unaesthetic odors and appearances, and to increase irritation to the skin and eyes.
On the other hand, long chain amine oxide surfactants have been freely used in acidic and alkaline cosmetics, toiletries and other consumer products. In alkaline products, amine oxide surfactants behave as nonionics; they bear neither positive nor negative molecular charges. The nonionic character allows them to be compatible with anionic ingredients in shampoos. Here, amine oxides can serve as foam contributors, foam stabilizes, viscosity enhancing agents, super fatting agents, etc. In nonionic and anionic hair conditioners, they can be employed as emulsifiers, thickeners and used for complementing typical fats, oils and waxes. The diversity of use of amine oxide surfactants are exemplified by the following disclosures.
In U.S. Pat. No. 3,990,991, aqueous shampoo-conditioner formulations are described comprising amphoteric, cryptoanionic and cationic surfactants. Amine oxides having surfactant properties are mentioned as useful cationic surfactants, although in the specific examples preferred quaternary ammonium compounds are employed in combination with an amine oxide. The pH of each such formulation is about 6.
In U.S. Pat. No. 4,007,261, conditioner compositions are described which consist essentially of an aqueous emulsion of an alkyl dimethyl amine oxide having from 16 to 22 carbon atoms in the alkyl chain, the pH of which compositions are preferably adjusted to between about 5.0 and 6.0. Specifically the invention encompasses pearlescent effects in such hair conditioners. However, it was found that such amine oxide formulations, namely the formulations having pH values described in this patent, did not provide adequate hair conditioning properties relative to quaternary ammonium surfactants. Augmentation of the amine oxide with quaternary ammonium compounds was required to impart good conditioning properties to formulations. See also, D&Cl, July 1981, pgs. 40-42, "Amine Oxides in Cosmetic Formulations", Klein, where "slightly acid pH" amine oxides were suggested as contributing to hair manageability.
U.S. Pat. No. 4,229,313 employs amine oxides as viscosity builders in cleaning and bleaching compositions for fabrics; both U.S. Pat. Nos. 4,4048,338 and 4,033,895 use amine oxides as counter-irritant ingredients in toiletry products to render them milder; U.S. Pat. No. 4,179,504 uses amine oxides as pharmacologically active ingredients in insecticidal and ovacidal preparations; U.S. Pat. No. 4,325,821 incorporates amine oxides into an improved froth flotation process to separate mineral ores; German Pat. No. 2,748,463 employs amine oxides as solubilizing agents for vitamin B derivatives in antiseborrheic products.
In acid media nonionic amine oxide surfactants acquire a positive charge through the inductive effects of hydrogen ions of the media. The amine oxides can behave cationic, however weakly cationic, since the positive charge produces less ionicity than that of quaternary ammonium salts of fatty amine salts. The positive charge, nevertheless, permits complete compatibility in cationic preparations and allows the cationicity of the amine oxide to support the cationicity of the dominant surfactant. An examination of the ingredient content of popular creme rinses, instant conditioners and balsams for hair sold on the market show that these products do not rely solely on amine oxides for conditioning. These acidic preparations employ quaternary ammonium surfactants and/or fatty amine salts, which are both strongly cationic, to produce hair conditioning. If amine oxides are present in the ingredient content, they are used for producing conditioning ancillary to the primary cationic surfactant as well as for other specific properties such as thickening, foaming, emulsification, etc. Amine oxide surfactants are recognized as not adsorbing to hair as strongly as quaternary ammonium surfactants and, therefore, do not produce as intense hair conditioning effects as quaternary ammonium salts.
Although it was known that amine oxides develop cationic properties, in other words a net positive charge, at low pH values for the reasons stated above, it has not been recognized that the cationic properties of amine oxides could be solely and usefully employed to condition hair in low pH media.